Dibromostyrene, which has been suggested as a flame retardant monomer, has a considerable tendency to undergo polymerization during storage. This polymerization tendency is greater than with styrene itself. It has been suggested in British Pat. No. 1,230,979, that dibromostyrene be stabilized with picric acid or a mixture of picric acid, and (i) a quinone such as hydroquinone or benzoquinone or (ii) a phenol such as tert-butyl-catechol.